This invention relates generally to security alarm systems, and more specifically, to security alarm systems for swimming pools and other contained bodies of liquid.
The number of drowning incidents in private swimming pools in the United States has reached tragic proportions in recent years. Drowning is particularly prevalent among young children who do not know how to swim, or are not capable of getting out of pools under emergency or accidental situations. Statistics show that about 3 to 5 children drown in private swimming pools each day.
Alarm systems designed for pools generally fall within three categories. The first category includes sensors activated by surface wave motion. Surface sensors comprise elements such as floatation devices. A major problem with floatation devices is the devices can be activated by wind or inanimate objects falling into the pool. Furthermore, floatation devices may be accidentally triggered by pool cleaning systems.
A second category includes hydrophones which detects splashing noises. A significant problem associated with hydrophones is that hydrophones can be activated with loud or low flying aircraft.
The third major category includes transducers secured below the pool's water surface. The transducers are activated when an object falling into the pool creates wave motions which propagate through the water. A problem with transducers, as with the other types of conventional security systems, is the sensor cannot distinguish a child from an inanimate object.
Attempts have been made to combine transducers, or the other types of conventional security systems, with other sensing devices. These have met with limited to poor success as evidenced by the lack of reliable pool security systems to date.